1. Field of the Invention
The present invention relates to a flip-flop circuit. The present invention also relates to a semiconductor device including the flip-flop circuit. Note that in this specification, a semiconductor device refers to a semiconductor element itself or a device including a semiconductor element.
2. Description of the Related Art
A flip-flop circuit is a circuit that can temporarily hold a specific logic state (hereinafter also referred to as data), and is used in a variety of semiconductor devices. For example, a flip-flop circuit is used as a circuit that temporarily holds data when the data is written or read to/from a storage circuit provided in a semiconductor device.
There are a variety of configurations of the flip-flop circuit described above; for example, a D flip-flop circuit illustrated in FIG. 11A is known.
The D flip-flop circuit illustrated in FIG. 11A includes an inverter 10, a transfer gate 12, a clocked inverter 14, an inverter 20, and an inverter 22. In FIG. 11A, “CLK_IN” and “CLKB_IN” represent a clock signal and an inverted signal of a clock signal, respectively. A clock signal CLK is input to the inverter 20, and the inverter 20 outputs the inverted signal CLKB_IN of the clock signal CLK. The inverted signal CLKB_IN of the clock signal CLK is input to the inverter 22, and the inverter 22 outputs the clock signal CLK_IN. The clock signal CLK_IN and the inverted signal CLKB_IN of the clock signal CLK are input to the transfer gate 12 and the clocked inverter 14.
FIG. 11B illustrates the configuration of the inverter 10, the inverter 20 and the inverter 22, FIG. 11C illustrates the configuration of the transfer gate 12, and FIG. 11D illustrates the configuration of the clocked inverter 14. The D flip-flop circuit illustrated in FIG. 11A includes 5 inverters, 2 transfer gates, and 2 clocked inverters, and thus is composed of 22 transistors ((2×5)+(2×2)+(4×2)) in total (see Patent Document 1).